Hybrid fuel cell

ABSTRACT

A hybrid fuel cell/battery including one or more electrochemical cell units comprising at least one cathode, at least one anode, and at least one auxiliary electrode. The auxiliary electrode works in combination with the anode to provide a current as a rechargeable battery while the anode and cathode work in combination to provide an electrical current as a fuel cell. The cathode and the auxiliary electrode may operate alone or in tandem to provide an electrical current.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation-in-part of, and is entitled tothe benefit of the earlier filing date and priority of, U.S. patentapplication Ser. No. 10/636,152, which is assigned to the same assigneeas the current application, entitled “A HYBRID FUEL CELL,” filed Aug. 7,2003, now U.S. Pat. No. 6,998,184 the disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention generally relates to fuel cells. Moreparticularly, the present invention relates to fuel cells having abuilt-in battery used to supplement the power output of the fuel celland provide instant start-up.

BACKGROUND

As the world's population expands and its economy increases, theincrease in the atmospheric concentrations of carbon dioxide is warmingthe earth causing climate changes. However, the global energy system ismoving steadily away from the carbon-rich fuels whose combustionproduces the harmful gas. Experts say atmospheric levels of carbondioxide may be double that of the pre-industrial era by the end of thenext century, but they also say the levels would be much higher exceptfor a trend toward lower-carbon fuels that has been going on for morethan 100 years. Furthermore, fossil fuels cause pollution and are acausative factor in the strategic military struggles between nations.Furthermore, fluctuating energy costs are a source of economicinstability worldwide.

In the United States, it is estimated, that the trend towardlower-carbon fuels combined with greater energy efficiency has, since1950, reduced by about half the amount of carbon spewed out for eachunit of economic production. Thus, the decarbonization of the energysystem is the single most important fact to emerge from the last 20years of analysis of the system. It had been predicted that thisevolution will produce a carbon-free energy system by the end of the21^(st) century. The present invention is another product which isessential to shortening that period to a matter of years. In the nearterm, hydrogen will be used in fuel cells for cars, trucks andindustrial plants, just as it already provides power for orbitingspacecraft. But, with the problems of storage and infrastructure solved(see U.S. application Ser. No. 09/444,810, entitled “A Hydrogen-basedEcosystem” filed on Nov. 22, 1999 for Ovshinsky, et al., which is hereinincorporated by reference and U.S. patent application Ser. No.09/435,497, entitled “High Storage Capacity Alloys Enabling aHydrogen-based Ecosystem,” filed on Nov. 6, 1999 for Ovshinsky et al.,which is herein incorporated by reference), hydrogen will also provide ageneral carbon-free fuel to cover all fuel needs.

Hydrogen is the “ultimate fuel.” In fact, it is considered to be “THE”fuel for the future. Hydrogen is the most plentiful element in theuniverse (more than 95%). Hydrogen can provide an inexhaustible, cleansource of energy for our planet which can be produced by variousprocesses. Utilizing the inventions of subject assignee, the hydrogencan be stored and transported in solid state form in trucks, trains,boats, barges, etc. (see the '810 and '497 applications).

A fuel cell is an energy-conversion device that directly converts theenergy of a supplied fuel into electric energy. Researchers have beenactively studying fuel cells to utilize the fuel cell's potential highenergy-generation efficiency. The base unit of the fuel cell is a cellhaving an oxygen electrode, a hydrogen electrode, and an appropriateelectrolyte. Fuel cells have many potential applications such assupplying power for transportation vehicles, replacing steam turbinesand power supply applications of all sorts. Despite their seemingsimplicity, many problems have prevented the widespread usage of fuelcells.

Fuel cells, like batteries, operate by utilizing electrochemicalreactions. Unlike a battery, in which chemical energy is stored withinthe cell, fuel cells generally are supplied with reactants from outsidethe cell. Barring failure of the electrodes, as long as the fuel,preferably hydrogen, and oxidant, typically air or oxygen, are suppliedand the reaction products are removed, the cell continues to operate.

Fuel cells offer a number of important advantages over internalcombustion engine or generator systems. These include relatively highefficiency, environmentally clean operation especially when utilizinghydrogen as a fuel, high reliability, few moving parts, and quietoperation. Fuel cells potentially are more efficient than otherconventional power sources based upon the Carnot cycle.

The major components of a typical fuel cell are the hydrogen electrodefor hydrogen oxidation and the oxygen electrode for oxygen reduction,both being positioned in a cell containing an electrolyte (such as analkaline electrolytic solution). Typically, the reactants, such ashydrogen and oxygen, are respectively fed through a porous hydrogenelectrode and oxygen electrode and brought into surface contact with theelectrolyte. The particular materials utilized for the hydrogenelectrode and oxygen electrode are important since they must act asefficient catalysts for the reactions taking place.

In a hydrogen-oxygen alkaline fuel cell, the reaction at the hydrogenelectrode occurs between hydrogen fuel and hydroxyl ions (OH⁻) presentin the electrolyte, which react to form water and release electrons:H₂+2OH⁻->2H₂O+2e⁻.At the oxygen electrode, oxygen, water, and electrons react in thepresence of the oxygen electrode catalyst to reduce the oxygen and formhydroxyl ions (OH⁻):O₂+2H₂O+4e⁻->4OH⁻.The flow of electrons is utilized to provide electrical energy for aload externally connected to the hydrogen and oxygen electrodes.

The catalyst in the hydrogen electrode of the alkaline fuel cell has tonot only split molecular hydrogen to atomic hydrogen, but also oxidizethe atomic hydrogen to release electrons. The overall reaction can beseen as (where M is the catalyst):M+H₂->2MH ->M+2H⁺+2e⁻.Thus the hydrogen electrode catalyst must efficiently dissociatemolecular hydrogen into atomic hydrogen. Using conventional hydrogenelectrode material, the dissociated hydrogen atoms are transitional andthe hydrogen atoms can easily recombine to form molecular hydrogen ifthey are not used very quickly in the oxidation reaction.

In a zinc-air fuel cell, a type of metal-air fuel cell, the reaction atthe anode occurs between the zinc contained in the anode and hydroxylions (OH⁻) present in the electrolyte, which react to release electrons:Zn->Zn⁺²+2e⁻Zn⁺²+2(OH⁻)->Zn(OH)₂Zn(OH)₂+2(OH)—->ZnO₂ ⁻²+2H₂OAt the cathode, oxygen, water, and electrons react in the presence ofthe oxygen electrode catalyst to reduce the oxygen and form hydroxylions (OH⁻):O₂+2H₂O+4e⁻->4OH⁻.The flow of electrons is utilized to provide electrical energy for aload externally connected to the hydrogen and oxygen electrodes.

Fuel cells, when used to power vehicles, are often used with anauxiliary battery pack because of the general inability of fuel cells toprovide power instantly upon start-up or provide increased bursts ofpower for sudden acceleration. Such vehicles are generally termed hybridelectric vehicles (HEV). The auxiliary battery supplements the fuel cellpower output during conditions requiring high power output, such asduring start-up or sudden acceleration. PEM fuel cells do not work verywell at low temperatures owing to the increase in the membraneresistance within the fuel cell at lower temperatures. In addition, thenormal start up time required for the PEM cell even at ambienttemperatures is quite significant making instant start difficult. UnlikePEM fuel cells, alkaline fuel cells are able to operate at ambienttemperatures, since they do not use any membranes and the electrolytedoes not freeze at temperatures above −60° C. Conventional alkaline fuelcells, however, still require the use of a battery during instantstart-up and sudden acceleration.

Hybrid systems have been divided into two broad categories, namelyseries and parallel systems. In a typical series system, a batterypowers an electric propulsion motor which is used to drive a vehicle,and an internal combustion engine is used to recharge the battery. In aparallel system, both the internal combustion engine and the batterypower in conjunction with an electric motor can be used, eitherseparately or together, to power a vehicle. In these types of vehicles,the battery is usually used only in short bursts to provide increasedpower upon demand after which the battery is recharged using theinternal combustion engine or via feedback from a regenerative brakingprocess.

There are further variations within these two broad categories. Onevariation is made between systems which are “charge depleting” in theone case and “charge sustaining” in another case. In the chargedepleting system, the battery charge is gradually depleted during use ofthe system and the battery thus has to be recharged periodically from anexternal power source, such as by means of connection to public utilitypower. In the charge sustaining system, the battery is recharged duringuse in the vehicle, through regenerative braking and also by means ofelectric power supplied from the a generator powered by the internalcombustion engine so that the charge of the battery is maintained duringoperation.

There are many different types of systems that fall within thecategories of “charge depleting” and “charge sustaining” and there arethus a number of variations within the foregoing examples which havebeen simplified for purposes of a general explanation of the differenttypes. However, it is to be noted in general that systems which are ofthe “charge depleting” type typically require a battery which has ahigher charge capacity (and thus a higher specific energy) than thosewhich are of the “charge sustaining” type if a commercially acceptabledriving range (miles between recharge) is to be attained in operation.

A key enabling technology for HEVs is having an energy storage systemhaving a high energy density while at the same time being capable ofproviding very high power. Such a system allows for recapture of energyfrom braking currents at very high efficiency while enabling the designof a smaller battery pack.

A typical auxiliary battery pack as used in HEV applications is a nickelmetal hydride battery pack. In general, nickel-metal hydride (Ni—MH)cells utilize a negative electrode comprising a metal hydride activematerial that is capable of the reversible electrochemical storage ofhydrogen. Examples of metal hydride materials are provided in U.S. Pat.Nos. 4,551,400, 4,728,586, and 5,536,591 the disclosures of which areincorporated by reference herein. The positive electrode of thenickel-metal hydride cell comprises a nickel hydroxide active material.The negative and positive electrodes are spaced apart in the alkalineelectrolyte.

Upon application of an electrical current across a Ni—MH cell, the Ni—MHmaterial of the negative electrode is charged by the absorption ofhydrogen formed by electrochemical water discharge reaction and theelectrochemical generation of hydroxyl ions:

The negative electrode reactions are reversible. Upon discharge, thestored hydrogen is released to form a water molecule and release anelectron.

The charging process for a nickel hydroxide positive electrode in analkaline electrochemical cell is governed by the following reaction:

After the first charge of the electrochemical cell, the nickel hydroxideis oxidized to form nickel oxyhydroxide. During discharge of theelectrochemical cell, the nickel oxyhydroxide is reduced to form betanickel hydroxide as shown by the following reaction:

While the inclusion of an auxiliary battery pack working in conjunctionwith a fuel cell has many advantages for powering vehicles, such systemsstill have disadvantages upon implementation in a vehicle. Thedisadvantages of including a battery along with the fuel cell mayinclude increased weight, space, terminals, inter cell connects, cost,maintenance, etc. Improvements in these areas will help fuel cells tobecome the standard source of power for vehicles and many otherapplications.

SUMMARY OF THE INVENTION

The present invention discloses a hybrid fuel cell comprising a fuelcell portion and a rechargeable battery portion both being disposed in agiven enclosure. The fuel cell portion and the rechargeable batteryportion are adapted to operate alone or in tandem to provide power. Thefuel cell portion and the rechargeable battery portion may share atleast one reactant. Such reactants may include hydrogen, oxygen, or themetal as used in the anode in a metal-air fuel cell. The hybrid fuelcell further comprises an anode section including one or more anodesdisposed between the fuel cell portion and the rechargeable batteryportion. The anode section may be shared between the fuel cell portionand the rechargeable battery portion.

The anode may be comprised of an anode active material including zinc,cadmium, magnesium, or aluminum. The anode may comprise 90 to 99 weightpercent of the anode active material and. 1 to 10 weight percent of abinder material. The anode may also include a hydrogen storage materialand/or Raney nickel. When including a hydrogen storage alloy and/orRaney nickel, the anode may comprise 0.0 to 88.0 weight percent of thehydrogen storage material, 0.0 to 88.0 weight percent Raney nickel, 4.0to 12.0 weight percent of a binder material, and 0.0 to 5.0 weightpercent of a conductive material. Where more than one anode is includedin the anode section, the composition of the anodes may vary as needed.The conductive material may be comprised of graphite or graphitizedcarbon and the hydrogen storage material may be comprised of Rare-earthmetal alloys, Misch metal alloys, zirconium alloys, titanium alloys,magnesium/nickel alloys, or mixtures thereof.

The fuel cell portion of the hybrid fuel cell comprises at least onecathode in electrical communication with the anode. The cathode maycomprise a carbon matrix with an active catalyst material catalytictoward the dissociation of molecular oxygen dispersed therein. Theactive catalyst material may be selected from silver, silver alloys,silver oxide, cobalt, cobalt oxide, cobalt manganese oxide, nickel,manganese oxide, manganese dioxide, pyrolyzed macro-cyclics, orcombinations thereof. The cathode may further include a peroxidedecomposing material.

The rechargeable battery portion comprises at least one auxiliaryelectrode in electrical communication with the anode. The auxiliaryelectrode may be a nickel electrode or a silver electrode. The auxiliaryelectrode comprises a positive electrode material. The positiveelectrode material may comprise 75 to 85 weight percent of a positiveelectrode active material, 0.0 to 10 weight percent cobalt, 0.0 to 10weight percent cobalt oxide, and 0.0 to 4.0 weight percent of a bindermaterial. The positive electrode active material may be selected fromnickel hydroxide/nickel oxyhydroxide, copper oxide, silver oxide,manganese dioxide, or combinations thereof.

The rechargeable battery portion may be adapted to accept an electricalcurrent from the fuel cell portion or a source of power external to thehybrid fuel cell. The fuel cell portion and the rechargeable batteryportion may also share an electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, shows an embodiment of a hydrogen-oxygen alkalineelectrochemical cell unit in accordance with the present invention.

FIG. 2, shows an exploded view of the electrochemical cell unit depictedin FIG. 1.

FIG. 3, shows an embodiment of a metal-air alkaline electrochemical cellunit in accordance with the present invention.

FIG. 4, shows an exploded view of the electrochemical cell unit depictedin FIG. 3.

FIG. 5, shows the performance during fuel cell mode and hybrid mode ofan embodiment of a hydrogen-oxygen hybrid fuel cell in accordance withthe present invention.

FIG. 6, shows the voltage of an embodiment of a hydrogen-oxygen hybridfuel cell in accordance with the present invention upon accepting acharging current.

FIG. 7, shows the performance during fuel cell mode and hybrid mode ofan embodiment of a metal-air hybrid fuel cell in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention discloses a hybrid fuel cell with an in siturechargeable battery, which can operate in 1) a fuel cell mode, 2) arechargeable battery mode, and 3) a hybrid mode which operates as acombined fuel cell/rechargeable battery. The hybrid fuel cell inaccordance with the present invention provides for power generation viaa fuel cell with the capability of supplementing the power produced fromthe fuel cell as needed with a built-in rechargeable battery. The hybridfuel cell may also work solely as a rechargeable battery as needed. Invehicle applications, the present invention provides for instantstart-up capability as well as increased power, which is needed forsudden acceleration. The present invention may also be useful for manyother applications requiring an instant source of power.

Each electrochemical cell unit includes a fuel cell portion and arechargeable battery portion. The fuel cell portion includes at leastone cathode, and the rechargeable battery portion includes at least oneauxiliary electrode. The fuel cell portion and the rechargeable batteryportion may share at least one reactant such as hydrogen and oxygen. Inthe case of a metal-air cell, the fuel cell portion and the rechargeablebattery portion may share a consumable metal such as zinc, aluminum,cadmium, or magnesium as found in the anode. The fuel cell portion andthe battery portion share a common anode section including at least oneanode. The cathode in the fuel cell portion and the anode in the anodesection work together as a fuel cell, while the auxiliary electrode inthe rechargeable battery portion and the anode in the anode section worktogether as a rechargeable battery. In addition, the cathode in the fuelcell portion and the auxiliary electrode in the rechargeable batteryportion may work together with the anode section simultaneously in“hybrid mode” thus providing higher power output. The anodes, cathodes,and auxiliary electrodes are in contact with an electrolyte, which maybe in liquid, gel, molten, or solid form. The fuel cell portion and therechargeable battery portion may also share a common electrolyte. Thebattery portion is recharged by accepting an electrical current from asource of power external to the hybrid fuel cell. The source of powermay be supplied from regenerative braking, solar power, a power supply,etc.

The anodes, cathodes, and auxiliary electrodes may be disposed. withinframes in the electrochemical cell units. The frames provide pathwaysfor oxygen, hydrogen, and/or electrolyte to contact the electrodes. Theframes may be constructed from any material resistant to the environmentwithin the electrochemical cell units. Examples of framed electrodes canbe found in U.S. patent application Ser. No. 10/284,817, entitled “FuelCell With Overmolded Electrode Assemblies”, filed on Oct. 31, 2002 forPuttaiah et al., the disclosure of which is herein incorporated byreference.

In many fuel cell systems, the fuel cell works in conjunction with anauxiliary battery pack as a hybrid vehicle system. The battery packprovides energy as needed and is recharged with energy from regenerativebraking and/or external power sources. The hybrid fuel cell inaccordance with the present invention is able to accept energy fromregenerative braking and/or external power sources resulting in chargingof the rechargeable battery portion. During normal operation, the anodesection and cathode in the fuel cell portion work together and functionlike a fuel cell, but upon increased power requirements, such as duringacceleration when used to power a vehicle, the anode section is able towork with the cathode in the fuel cell portion as a fuel cell whileworking with the auxiliary electrode in the rechargeable battery portionas a rechargeable battery thereby providing instant high power outputthrough an increase in current density and/or a decrease inpolarization. The rechargeable battery portion may also work alone withthe anode section to provide power. The capability of the rechargeablebattery portion to work alone is especially useful in vehicleapplications for instant startup.

The fuel cell portion of the electrochemical cell units in accordancewith the present invention may be designed to operate as ahydrogen-oxygen alkaline fuel cell, a metal-air fuel cell, a PEM fuelcell, a direct methanol fuel cell, a molten carbonate fuel cell, a solidoxide fuel cell, or a phosphoric acid fuel cell, provided that all ofthe electrodes including the auxiliary electrode in the rechargeablebattery portion are compatible with the working conditions, and theappropriate electrolyte and temperatures are selected. Preferably, thefuel cell portion of the electrochemical cell units operate as ahydrogen-oxygen alkaline fuel cell or metal-air cell.

A first embodiment of an electrochemical cell unit 10 in accordance withthe present invention is shown in FIG. 1 and FIG. 2. The electrochemicalcell unit operates as a hybrid hydrogen-oxygen alkaline fuelcell/rechargeable battery. The electrochemical cell unit includes twofuel cell portions each including one cathode 11 having an oxygeninterface and an electrolyte interface, and a rechargeable batteryportion including one auxiliary electrode 12 at least partially immersedin an electrolyte. Each fuel cell portion shares an anode section withthe rechargeable battery portion. The anode sections each include atleast one anode 13. When two anodes are utilized in the anode sectioneach anode has a hydrogen interface and an electrolyte interface, withthe two anodes being separated by a gas distribution plate 14 adjacentto the hydrogen interfaces of each anode. Hydrogen is supplied underpressure to the hydrogen interface of the anodes 13 via the gasdistribution plate 14, which uniformly distributes the hydrogen acrossthe hydrogen interface of the anode 13. When one anode is utilized inthe anode section, both sides of the electrode serve as an electrolyteinterface in contact with an electrolyte, while hydrogen flows throughflow channels within the anode. Air is supplied as a source of oxygen tothe oxygen interface of the cathodes 11 in the fuel cell portions fromthe atmosphere via a concentration gradient as oxygen is consumed at theoxygen interface of the cathode. Alternatively, oxygen may be suppliedto the oxygen interface of the cathode 11 under pressure via gasdistribution plates positioned adjacent to the oxygen interface of thecathode, however, it is preferred that the oxygen be supplied to theoxygen interface from the atmosphere at atmospheric conditions. Thecathodes 11 and the anodes 13 are preferably separated by an electrolytedistribution plate 15 positioned between the electrolyte interface ofthe cathode and the electrolyte interface of one of the anodes. Theelectrolyte distribution plate 15 distributes the electrolyte across theelectrolyte interfaces of one of the anodes 13 and the cathode 11 whileproviding mechanical support to the electrochemical cell unit. Theauxiliary electrode 12 and the anodes 13 adjacent to the auxiliaryelectrode in the anode sections are preferably separated by a batteryseparator 16. The battery separator 16 is designed to prevent a shortcircuit from occurring between the auxiliary electrode 12 and the anodesection while maintaining a certain level of electrolyte in contact withthe auxiliary electrode and the electrolyte interface of the anode 13facing the auxiliary electrode 12. The battery separator 16 may alsoprovide support to the electrochemical cell unit 10. Endplates 17 usedto provide support to the electrochemical cell unit 10 are positionedadjacent to the oxygen interfaces of the cathodes to complete theelectrochemical cell unit. The endplates 17 are preferably designed toallow air from the atmosphere to contact the oxygen interfaces of thecathodes, thus providing the cathodes with a source of oxygen, however,the endplates may be designed such that a gas distribution plate isplaced between the endplate and the oxygen interface of the cathodes,whereby the gas distribution plate is supplied with an oxygen containingstream and distributes the oxygen containing stream across the oxygeninterface. The gas distribution plates, electrolyte distribution plates,battery separators, and endplates may be formed from any material ableto withstand the environment within the electrochemical cell units andmay have many different design configurations provided they are able tosatisfy their intended purpose.

During operation, hydrogen enters or is absorbed by the anodes 13through the hydrogen interface and reacts with the electrolytedistributed across the electrolyte interface of the anodes via theelectrolyte distribution plates 15 to form water and electrons. Oxygenenters the oxygen interface of the cathode 11, is dissociated intoatomic oxygen, and reacts electrochemically to form hydroxyl ions at theelectrolyte interface of the cathode 11. The electrons flowing from theanode 13 to the cathode 11 form the electrical current supplied to thedesired application. When a sudden surge of additional power is needed,electrical current may be supplied from the rechargeable batteryportion. The auxiliary electrode 12 contained in the rechargeablebattery portion works with the anode 13 adjacent to the auxiliaryelectrode 12 in the anode section to provide an electrical current asneeded. The auxiliary electrode 12 is fully charged when it is in itsoxidized state. Upon discharge, the auxiliary electrode 12 undergoesreduction thereby providing an electrical current. The electricalcurrent may be used to supplement the current produced by the fuel cellor may be used to provide power alone. To recharge the rechargeablebattery portion, a current is applied across the anode adjacent to theauxiliary electrode and auxiliary electrode to reoxidize the auxiliaryelectrode.

The anodes 13 and cathodes 11 may be designed such that oxygen orhydrogen enters through the edge of the electrode and flows through theelectrode, or each electrode may have an oxygen or hydrogen contactingside and an electrolyte contacting side. In either case, the electrolyteinterfaces of the cathodes and anodes are in constant contact with anelectrolyte, while the auxiliary electrode is at least partiallysubmerged in the electrolyte. For the anodes and cathodes to workproperly, the electrochemical cell should be designed such that thehydrogen or oxygen interfaces on one side of the cathodes or anodes orwithin the cathodes or anodes (as is the case with flow channels withinthe electrode) remain dry and constantly supplied with hydrogen oroxygen during operation.

A second embodiment of an electrochemical cell unit 10 a in accordancewith the present invention is depicted in FIG. 3 and FIG. 4. The secondembodiment operates as a hybrid metal-air fuel cell/rechargeablebattery. The hybrid metal-air fuel cell may operate in an aqueous ornonaqueous electrolyte environment. The electrochemical cell unit 10 aincludes two fuel cell portions each including one cathode 11 having anoxygen interface and an electrolyte interface, and a rechargeablebattery portion including one auxiliary electrode 12. Each fuel cellportion shares an anode section with the rechargeable battery portion.The anode sections each include at least one consumable anode 13 a. Theconsumable anode 13 a and the auxiliary electrode 12 are at leastpartially submerged in an electrolyte solution. Unlike the hybridhydrogen-oxygen alkaline fuel cell, the consumable anode 13 a for themetal-air cell does not need to be supplied with hydrogen. Air issupplied as a source of oxygen to the oxygen interface of the cathodesin the fuel cell portions from the atmosphere via a concentrationgradient, as oxygen is consumed at the oxygen interface of the cathode.Alternatively, oxygen may be supplied to the oxygen interface of thecathode 11 under pressure via gas distribution plates (as described inthe first embodiment) positioned adjacent to the oxygen interface of thecathode, however, it is preferred that the oxygen be supplied to theoxygen interface from the atmosphere at atmospheric conditions.

The consumable anode 13 a, serving as a solid fuel, is positionedbetween the cathode 11 of the fuel cell portions and the auxiliaryelectrode 12 of the battery portion with the electrolyte contacting sideof the cathodes 11 facing the consumable anodes 13 a. The cathodes 11and the consumable anodes 13 a are preferably separated by anelectrolyte distribution plate 15 positioned between the electrolyteinterface of the cathode 11 and the consumable anodes 13 a. Theelectrolyte distribution plate 15 distributes the electrolyte across theelectrolyte interface of the cathodes 11 and face of the consumableanodes 13 a adjacent to the cathodes while providing mechanical supportto the electrochemical cell unit 10 a. The auxiliary electrode 12 andthe consumable anodes 13 a are preferably separated by a batteryseparator 16 designed to prevent a short circuit from occurring betweenthe auxiliary electrode 12 and the consumable anodes 13 a whilemaintaining a certain level of electrolyte in contact with the auxiliaryelectrode and the face of the consumable anodes facing the auxiliaryelectrode. The battery separator 16 may also provide mechanical supportto the electrochemical cell unit. End plates 17 are typically placed atthe ends of each electrochemical cell unit 10 a. The endplates 17 arepreferably designed to allow air from the atmosphere to contact theoxygen interfaces of the cathodes, thus providing the cathodes with asource of oxygen, however, the endplates may be designed such that a gasdistribution plate (as described in the first embodiment) is placedbetween the endplate and the oxygen interface of the cathodes, wherebythe gas distribution plate is supplied with an oxygen containing streamand distributes the oxygen containing stream across the oxygeninterface. The gas distribution plates, electrolyte distribution plates,battery separators, and endplates may be formed from any material ableto withstand the environment within the electrochemical cell units andmay have many different design configurations provided they are able tosatisfy their intended purpose.

The cathodes 11 may be designed such that oxygen enters through the edgeof the electrode and flows through the electrode, thus removing the needfor gas distribution plates, or each cathode may have an oxygencontacting side and an electrolyte contacting side. In either case, theelectrolyte interfaces of the cathodes are in constant contact with anelectrolyte, while the auxiliary electrode is at least partiallysubmerged in the electrolyte. For the cathodes to work properly, theelectrochemical cell should be designed such that the oxygen interfaceson one side of the cathodes or within the cathodes (as is the case withflow channels within the electrode) remain dry allowing a constantsupply of oxygen during operation.

During operation, oxygen enters the oxygen interface of the cathode 11,is dissociated into atomic oxygen, and reacts with water and electronsto form hydroxyl ions at the electrolyte interface of the cathode 11.The consumable anode 13 a and cathode 11 of the electrochemical cellunit 10 a provide an electrical current resulting from the production ofelectrons from the oxidation of the anode metal within the consumableanode, such as zinc as used in aqueous cells. When additional power isneeded, electrical current may be supplied from the auxiliary electrode12 coupled with the consumable anode 13 a. The auxiliary electrode 12 isfully charged when in its oxidized state. Upon discharge, the auxiliaryelectrode 12 undergoes reduction thereby completing the circuit andproviding an electrical current. The electrical current may be used tosupplement the current produced by the fuel cell or may be used alone.To recharge the auxiliary electrode as well as the consumable anode, acurrent is applied across the consumable anode and auxiliary electrodeto reoxidize the auxiliary electrode. During reduction of the auxiliaryelectrode, metal ions contained in the electrolyte solution are reducedand deposited back onto the consumable anode as metal therebyreplenishing the metal consumed by the fuel cell portion duringoperation of the electrochemical cell unit. Additives may also be addedto the anode or the electrolyte to reduce the formation of dendrites andensure a smooth uniform metallic plating when the metal is deposited onthe consumable anode.

Anodes as used in the hybrid hydrogen-oxygen alkaline fuel cellembodiment of the present invention are generally comprised of an activematerial supported on a current collector grid. The active material forthe anode of the hybrid hydrogen-oxygen alkaline fuel cell may begenerally comprised of 0.0 to 88.0 weight percent of a hydrogen storagematerial, 0.0 to 88.0 weight percent Raney Nickel, 4.0 to 12 weightpercent binder material, and 0.0 to 5.0 weight percent graphite orgraphitized carbon. The hydrogen storage material may be selected fromRare-earth metal alloys, Misch metal alloys, zirconium alloys, titaniumalloys, magnesium/nickel alloys, and mixtures or alloys thereof whichmay be AB, AB₂, or AB₅ type alloys. Such alloys may include modifierelements to increase their hydrogen storage capability.

Consumable anodes as used in the hybrid metal-air fuel cell embodimentof the present invention are generally comprised of an active materialsupported on a current collector grid. When utilizing an aqueouselectrolyte within the hybrid metal-air fuel cell, the active materialfor the anode is typically comprised of an anode metal such as zinc,aluminum, magnesium, cadmium, iron, alloys or combinations thereof.Typically these anode metals may contain between 1 to 10 weight percentof indium, bismuth, lead, tin, or mercury. When utilizing a nonaqueouselectrolyte within the hybrid metal-air fuel cell, the active materialfor the anode may comprise an anode metal such as lithium. The activematerial for the anodes as used in the hybrid metal-air fuel cell inaccordance with the present invention may be generally comprised of 90to 99 weight percent of an anode metal, and 1.0 to 10 weight percentbinder material.

The binder materials may be any material, which binds the activematerial together to prevent degradation or disintegration of theelectrode/electrode materials during the lifetime of the electrodes.Binder materials should be resistant to the environment present withinthe electrochemical cell units. This includes high concentration of KOH,dissolved oxygen, dissolved peroxyl ions (HO₂ ⁻), etc. Examples ofadditional binder materials, which may be added to the activecomposition, include, but are not limited to, polymeric binders such aspolyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) andhydroxycarboxymethyl cellulose (HCMC). Other examples of polymericbinders include fluoropolymers. An example of a fluoropolymer ispolytetrafluoroethylene (PTFE). Other examples of additional bindermaterials, which may be added to the active composition, includeelastomeric polymers such as styrene-butadiene. In addition, dependingupon the application, additional hydrophobic materials and/orelectroconductive plastics may also be added to the active composition.An example of an electroconductive polymeric binder material iscommercially sold under the name Panipol.

The cathodes may be comprised of any materials generally used inhydrogen-oxygen alkaline fuel cells or metal-air fuel cells capable ofwithstanding the operating conditions within the electrochemical cell.The cathodes may be designed to operate with an aqueous or nonaqueouselectrolyte depending on the type of anode being used. The cathodes asused in hydrogen-oxygen alkaline fuel cells or aqueous metal-air cellsare typically comprised of a carbon matrix with a material catalytictoward the dissociation of molecular oxygen into atomic oxygen dispersedtherein. A single layered cathode may be comprised of a carbon matrixwith an active catalytic material dispersed therein, with the carbonmatrix being supported by at least one current collector grid. Amultilayered cathode may be composed of an active material layer havinga built-in hydrophobic character, a gas diffusion layer having a greaterbuilt-in hydrophobic character than the active material layer, and atleast one current collector grid. The active material layer and the gasdiffusion layer are positioned adjacent to each other and supported byat least one current collector grid. The gas diffusion layer is composedof a teflonated carbon matrix. The teflonated carbon matrix may becomprised of 40% teflonated acetylene black carbon or 60% teflonatedVulcan XC-72 carbon (Trademark of Cabot Corp.). The active materiallayer of the cathode in accordance with the present invention iscomposed of carbon particles coated with PTFE. The carbon particles arepreferably carbon black particles, such as Black Pearl 2000 (Trademarkof Cabot Corp.). The carbon/PTFE black mixture contains approximately 10to 20 percent PTFE with the remainder being carbon black particles. Anactive material catalytic toward the dissociation of molecular oxygeninto atomic oxygen is dispersed throughout the active material layer.The active catalyst material may be selected from silver metal, silveralloys, silver oxide, cobalt oxide, cobalt manganese oxide, cobalt,nickel, manganese oxides, manganese dioxide, pyrolyzed macro-cyclics, orcombinations thereof. The active material layer may also include up to30 weight percent of a peroxide decomposing material. The peroxidedecomposing material may be selected from MnO₂, MnO, cobalt oxides,nickel oxides, iron oxides, or mixtures thereof.

The active catalyst material may be incorporated into the activematerial layer by mechanically mixing the active catalyst material withthe teflonated carbon prior to forming the electrode, or the activecatalyst material may be impregnated into the active material layerafter formation of the electrode. To impregnate the active materiallayer of the cathode with the active catalyst material after electrodeformation, the active catalyst material may be chemically orelectrochemically impregnated into the active material layer. Tochemically or catalytically impregnate the active material layer of thecathode, the cathode is dipped into an aqueous solution of an activecatalyst material precursor. The active catalyst material precursor maybe a 1M AgNO₃ solution containing 10% by weight sugar as a reducingagent. Other precursors such as a AgNO₃/Ga(NO)₃ mixture, AgNO₃/LiNO₃mixture, Co(NO₃)₂, a cobalt amine complex, NI(NO₃)₂, Mn(NO₃)₂, cyanocomplexes, organo metallic complexes, amino complexes,citrate/tartrate/lactate/oxalate complexes, transition metal complexes,transition metal macro-cyclics, and mixtures thereof may be substitutedfor the AgNO₃ in the precursor solution. Once submerged in the aqueousactive catalyst material precursor solution, the solution may be pulledinto the active material layer under vacuum. The varying layers ofhydrophobicity between the gas diffusion layer and the active materiallayer allow the solution to penetrate into the pores within the activematerial layer and not penetrate into the gas diffusion layer. Theactive catalyst material is deposited from the aqueous solution in thepores within the active material layer and any air or gases present inthe solution pass through the gas diffusion layer. In addition todipping in the aqueous solution, the impregnation may be performed byspraying or spreading the active catalyst on the electrode surface.After removing the cathode from the active catalyst material solution,the cathode is dried at room temperature. The cathode is then heattreated at 50 degrees Celsius to remove any water from the electrode.The cathode may then be heat treated at 300-375 degrees Celsius for halfan hour to decompose any remaining metal nitrates into theircorresponding oxides. Temperatures exceeding this range are not employedbecause the teflon binder will begin to decompose and adversely affectthe performance of the electrodes. Depending upon the catalyst used,these oxides may further decompose to produce their parent metalcatalysts. To add more catalyst the above process is repeated asnecessary. The cathode is then cooled and ready for use. Afterimpregnation, the active catalyst material forms submicron to nanoparticles of the active catalyst material within the carbon matrix.

The auxiliary electrode may be comprised of any battery positiveelectrode material capable of withstanding the operating conditionswithin the electrochemical cell. The auxiliary electrode may be designedto operate with an aqueous or nonaqueous electrolyte depending on thetype of anode being used. The auxiliary electrodes are generallycomposed of a positive electrode material supported on a currentcollector grid. The aqueous positive electrode active material and thenonaqueous positive electrode active material may be any material thatmay undergo oxidation upon charging and reduction upon discharging ofthe electrochemical cell. The positive electrode material, for use withan aqueous electrolyte, is generally comprised of 75 to 85 weightpercent positive electrode active material, 0.0 to 10 weight percentcobalt, 0.0 to 10 weight percent cobalt oxide, and 0.0 to 4.0 weightpercent binder material. The aqueous positive electrode active materialmay be selected from nickel hydroxide/nickel oxyhydroxide, copper oxide,silver (I or II) oxide, or manganese dioxide. When utilizing anonaqueous electrolyte, to facilitate lithium intercalation, thepositive electrode material may be made up entirely of the nonaqueouspositive electrode active material. The positive electrode material,however, may also be comprised of 84 weight percent active material, 4.0weight percent graphite, 4.0 weight percent acetylene black, and 8.0weight percent of a binder material. The nonaqueous positive electrodeactive material may be selected from LiCoO₂, LiMn₂O₄, LiMnO₂,LiNi_(0.5)1.5O₄. For thin film nonaqueous cells, LiCoO₂ or LiMn₂O₄ aregenerally sputtered on nickel or platinum based current collectors. Thebinder materials as used in the auxiliary electrodes may be any of thoselisted for the anode and cathode.

The electrodes in accordance with the present invention may bepaste-type electrodes or non paste-type electrodes. Non-paste typeelectrodes may be powder compacted, sinteredchemically/electrochemically impregnated, or plastic bonded extrudedtype. Paste-type electrodes may be formed by applying a paste of theactive electrode material onto a conductive substrate, compressing apowdered active electrode material onto a conductive substrate, or byforming a ribbon of the active electrode material and affixing it onto aconductive substrate. The substrate as used in accordance with thepresent invention may be any electrically conductive support structurethat can be used to hold the active composition such as a currentcollector grid selected from, but not limited to, an electricallyconductive mesh, grid, foam, expanded metal, or combinations thereof.The most preferable current collector grid is an electrically conductivemesh having 40 wires per inch horizontally and 20 wires per inchvertically, although other meshes may work equally well. The wirescomprising the mesh may have a diameter between 0.005 inches and 0.01inches, preferably between 0.005 inches and 0.008 inches. This designprovides optimal current distribution due to the reduction of the ohmicresistance. Where more than 20 wires per inch are vertically positioned,problems may be encountered when affixing the active material to thesubstrate. The actual form of the substrate used may depend on whetherthe substrate is used for the positive or the negative electrode of theelectrochemical cell, the type of electrochemical cell (for example,battery or fuel cell), the type of active material used, and whether itis paste type or non-paste type electrode. The conductive substrate maybe formed of any electrically conductive material and is preferablyformed of a metallic material such as a pure metal or a metal alloy.Examples of materials that may be used include nickel, nickel alloy,copper, copper alloy, nickel-plated metals such as nickel-plated copperand copper-plated nickel. The actual material used for the substratedepends upon many factors including whether the substrate is being usedfor the positive or negative electrode, the type of electrochemical cell(for example battery or fuel cell), the potential of the electrode, andthe pH of the electrolyte of the electrochemical cell.

In a paste type electrode, the active electrode composition is firstmade into a paste. This may be done by first making the active electrodecomposition into a paste, and then applying the paste onto a conductivesubstrate. A paste may be formed by adding water and a “thickener” suchas carboxymethyl cellulose (CMC) or hydroxypropylmethyl cellulose (HPMC)to the active composition. The paste would then be applied to thesubstrate. After the paste is applied to the substrate to form theelectrode, the electrode may be sintered. The electrode may optionallybe compressed prior to sintering.

To form the electrodes by compressing the powdered active electrodematerial onto the substrate, the active electrode material is firstground together to form a powder. The powdered active electrode materialis then pressed or compacted onto a conductive substrate. Aftercompressing the powdered active electrode material onto the substrate,the electrode may be sintered. To form the electrodes using ribbons ofthe active electrode material, the active electrode material is firstground into a powder and placed into a roll mill. The roll millpreferably produces a ribbon of the active electrode material having athickness ranging from 0.018 to 0.02 inches, however, ribbons with otherthicknesses may be produced in accordance with the present invention.Once the ribbon of the active electrode material has been produced, theribbon is placed onto a conductive substrate and rerolled in the rollmill to form the electrode. After being rerolled, the electrode may besintered.

The electrode may be sintered in the range of 170 to 180° C. so as notto decompose the conductive polymer, as compared to sinteringtemperatures in the range of 310° C. to 330° C. if the conductivepolymer is not utilized in the electrode.

EXAMPLE 1

A hybrid hydrogen-oxygen alkaline fuel cell in accordance with thepresent invention was constructed and tested. The hybrid hydrogen-oxygenalkaline fuel cell included a cathode, two anodes, and an auxiliaryelectrode. One of the anodes was constructed to operate with the cathodeas a fuel cell and the other anode was constructed to operate with theauxiliary electrode as a battery.

The cathode for the hybrid hydrogen-oxygen alkaline fuel cell wasprepared by first depositing the gas diffusion layer composed of 45weight percent teflonated carbon (acetylene black Shawinigan AB) onto acurrent collector grid. Approximately 6-10 g of gas diffusion layermaterial was deposited onto the current collector grid per 100 cm². Theactive material layer composed of 20 weight percent teflonated carbon(Black Pearl 2000, trademark of Cabot Corp.) was then deposited onto thegas diffusion layer. Approximately 2-3 grams of active material layermaterial is deposited onto the gas diffusion layer per 100 cm². Afterdepositing the gas diffusion layer, a second current collector grid isplaced on top of the active material layer to complete the cathode. Thecathode was hot pressed at a pressure of 0.3 tons per cm² for twominutes after the temperature was reached. The cathode was subsequentlycooled to room temperature.

The active material layer of the cathode was then impregnated with anactive catalyst material. The cathode was dipped into an aqueoussolution of an active catalyst material precursor. The active catalystmaterial precursor was a 1M AgNO₃ solution preceded by a 10 percent byweight sugar solution dip as a reducing agent. Once submerged in theaqueous active catalyst material precursor solution, the solution waspulled into the active material layer under vacuum. The varying layersof hydrophobicity between the gas diffusion layer and the activematerial layer allowed the solution to penetrate into the pores withinthe active material layer and not penetrate into the gas diffusionlayer. After removing the cathode from the active catalyst materialsolution, the cathode was dried at room temperature. The cathode wasthen heat treated at 50 degrees Celsius to remove any water from theelectrode. The cathode was then heat treated at 300-375 degrees Celsiusfor half an hour to decompose any remaining nitrates into oxides. Thecathode was then cooled and incorporated into the hybrid hydrogen-oxygenalkaline fuel cell.

The anode designed to operate with the cathode as a fuel cell included agas diffusion layer and an active material layer. The gas diffusionlayer was composed of 40% teflonated carbon rolled into a ribbon. Theactive material layer was prepared by forming a mixture composed of 88weight percent Raney nickel, 8.0 weight percent teflon, and 4.0 weightpercent graphite (Timcal KS 75). The mixture was then rolled intoribbons of active anode material. The active material layer ribbon andthe gas diffusion layer ribbon were placed between two current collectorgrids and re-rolled to form the hydrogen electrode. The anode wassintered in nitrogen at 350° C. for half an hour then cooled to roomtemperature in a nitrogen environment.

The anode designed to operate with the auxiliary electrode also includeda gas diffusion layer and an active material layer. The gas diffusionlayer was prepared in the same manner as the gas diffusion layer for theanode designed to operate with the cathode. The active material layer,however, was formed from a mixture composed of 88 weight percent Mischmetal, 8.0 weight percent teflon, and 4.0 weight percent graphite. Themixture was then rolled into ribbons of active anode material. Theactive material layer ribbon and the gas diffusion layer ribbon wereplaced between two current collector grids and re-rolled to form thehydrogen electrode. The anode was sintered in nitrogen at 350° C. forhalf an hour then cooled to room temperature in a nitrogen environment.

The auxiliary electrode was prepared by first forming a standard pastecomposed of 88.6 weight percent nickel hydroxide material withco-precipitated zinc and cobalt from Tanaka Chemical Company, 5.0 weightpercent cobalt, 6.0 weight percent cobalt oxide, and 0.4 weight percentpolyvinyl alcohol binder. The paste was then affixed to a currentcollector grid to form the auxiliary electrode.

The hybrid hydrogen-oxygen alkaline fuel cell was tested underdischarging conditions and tested for recharging capability. The resultsfor the hybrid hydrogen-oxygen alkaline fuel air cell are shown in FIG.5, FIG. 6, and below in Table 1. FIG. 5 shows the current (dashed line)and the voltage of the fuel cell only and the voltage of the fuel celland battery together. The voltages were measured during a 3 A dischargeand a 20 second pulse discharge of 9.6 A. The hybrid hydrogen-oxygenalkaline fuel cell achieved an increased voltage when both the cathodeand the auxiliary electrode battery operated in tandem with therespective anodes as compared to the cathode operating alone with therespective anode. FIG. 6 shows voltage (□) of the hybrid fuel cell whena pulse current (⋄) is applied to the cell. The voltage of the hybridcell steadily increased upon receiving a series of 30 second 1 amperepulse charges.

TABLE 1 At 10 sec. 3 A pulse At 10 sec. 9.6 A pulse dischargingdischarging Cathode Only Cell voltage: 0.7095 V Cell Voltage: 0.2759 VCathode and Cell Voltage: 1.1080 V Cell Voltage: 0.8782 V Auxiliaryelectrode ΔV 0.3985 V 0.5723 V Voltage % increase 55.8% 207%

EXAMPLE 2

A hybrid metal air fuel cell in accordance with the present inventionwas constructed and tested. The hybrid metal-air fuel cell included acathode, an anode, and an auxiliary electrode. The anode was designed tooperate with the cathode as a fuel cell and operate with the auxiliaryelectrode as an battery.

The cathode for the hybrid metal-air fuel cell was prepared by firstdepositing the gas diffusion layer composed of 60 weight percentteflonated carbon (Vulcan XC-72) onto a current collector grid.Approximately 6-10 g of gas diffusion layer material was deposited ontothe current collector grid per 100 cm². The active material layercomposed of 20 weight percent teflonated carbon was then deposited ontothe gas diffusion layer. Approximately 2-3 grams of active materiallayer material is deposited onto the gas diffusion layer per 100 cm².After depositing the gas diffusion layer, a second current collectorgrid is placed on top of the active material layer to complete thecathode. The cathode was then hot pressed at a pressure of 0.3 tons percm² and subsequently cooled to room temperature.

The active material layer of the cathode was then impregnated with anactive catalyst material. The cathode was dipped into an aqueoussolution containing 10 weight percent sugar as a reducing agent prior todipping in the active catalyst material precursor solution. The activecatalyst material precursor was a 1M AgNO₃ solution. Once submerged inthe aqueous active catalyst material precursor solution, the solutionwas pulled into the active material layer under vacuum. The varyinglayers of hydrophobicity between the gas diffusion layer and the activematerial layer allowed the solution to penetrate into the pores withinthe active material layer and not penetrate into the gas diffusionlayer. After removing the cathode from the active catalyst materialsolution, the cathode was dried at room temperature. The cathode wasthen heat treated at 50 degrees Celsius to remove any water from theelectrode. The cathode was then heat treated at 300-375 degrees Celsiusfor half an hour to decompose any remaining nitrates into oxides. Thecathode was then cooled and incorporated into the hybrid metal-air fuelcell.

The anode for the hybrid metal-air fuel cell was prepared by forming amixture composed of 98.7 weight percent zinc powder, 1.0 weight percentteflon, and 0.3 weight percent carboxymethyl cellulose and then mixed toform a paste. The paste was then applied onto nickel foam, dried and afinal roll compaction to the desired electrode thickness of 0.02 inches.

The auxiliary electrode was prepared by first forming a standard pastecomposed of 88.6 weight percent nickel hydroxide material withco-precipitated zinc and cobalt from Tanaka Chemical Company, 5.0 weightpercent cobalt, 6.0 weight percent cobalt oxide, and 0.4 weight percentpolyvinyl alcohol binder. The paste was then affixed to a currentcollector grid to form the auxiliary electrode.

The hybrid metal air cell was tested under discharging conditions. Theresults for the hybrid metal air fuel cell are shown in FIG. 7 and belowin Table 2. FIG. 6 shows the current (dashed line) and the voltage ofthe fuel cell only and the voltage of the fuel cell and batterytogether. The voltages were measured during a 3 A discharge and a 20second pulse discharge of 9.6 A. The hybrid metal air cell achieved anincreased voltage when both the cathode and the auxiliary electrodebattery operated in tandem with the anode as compared to the cathodeoperating alone with the anode.

TABLE 2 At 10 sec. 3 A pulse At 10 sec. 9.6 A discharging pulsedischarging Cathode Only Cell voltage: 1.1096 V Cell Voltage: 0.7531 VCathode and Auxi- Cell Voltage: 1.5725 V Cell Voltage: 1.3507 V liaryelectrode ΔV 0.4629 V 0.5976 V Voltage % increase 41.7% 79.4%

The foregoing is provided for purposes of explaining and disclosingpreferred embodiments of the present invention. Modifications andadaptations to the described embodiments, particularly involving changesto the shape of the fuel cell and components thereof and varyingelectrode compositions will be apparent to those skilled in the art.These changes and others may be made without departing from the scope orspirit of the invention in the following claims.

1. A hybrid fuel cell including one or more electrochemical cell units,said electrochemical cell units each comprising: an auxiliary electrodehaving a first side and a second side; a first anode pair and a secondanode pair, said first and second anode pairs each comprising two anodeshaving a hydrogen interface and an electrolyte interface, said anodes insaid first anode pair and said second anode pair being separated by ahydrogen distribution plate disposed between said anodes such that saidhydrogen interfaces of said anodes face each other and the electrolyteinterfaces face outward from said first anode pair and said second anodepair, said hydrogen distributor plates being adapted to receive anddistribute a supply of hydrogen across said hydrogen interfaces of saidanodes; a first cathode and a second cathode, said first cathode andsaid second cathode each having an oxygen contacting surface and anelectrolyte contacting surface; a first battery separator and a secondbattery separator; and a first gas distributor plate and a second gasdistributor plate; said auxiliary electrode being positioned such thatsaid first battery separator is disposed adjacent to said first side ofsaid auxiliary electrode and said second battery separator is disposedadjacent to said second side of said auxiliary electrode; said firstanode pair being disposed adjacent to said first battery separatoropposite said auxiliary electrode and said second anode pair beingdisposed adjacent to said second battery separator opposite saidauxiliary electrode; said first electrolyte distributor plate beingdisposed adjacent to said first anode pair opposite said first batteryseparator and said second electrolyte distributor plate being disposedadjacent to said second anode pair opposite said second batteryseparator, said first cathode being disposed adjacent to said firstelectrolyte distributor plate opposite said first anode pair such thatsaid electrolyte contacting surface of said first cathode faces saidfirst anode pair and said second cathode being disposed adjacent to saidsecond electrolyte distributor plate opposite said second anode pairsuch that said electrolyte contacting surface of said second cathodefaces said second anode pair.
 2. The hybrid fuel cell according to claim1, wherein said anodes comprise a hydrogen storage material and/or Raneynickel.
 3. The hybrid fuel cell according to claim 2, wherein saidanodes comprise 0.0 to 88.0 weight percent of said hydrogen storagematerial, 0.0 to 88.0 weight percent Raney nickel, 4.0 to 12.0 weightpercent of a binder material, and 0.0 to 5.0 weight percent of aconductive material.
 4. The hybrid fuel cell according to claim 3,wherein said hydrogen storage material comprises Rare-earth metalalloys, Misch metal alloys, zirconium alloys, titanium alloys,magnesium/nickel alloys, or mixtures thereof.
 5. The hybrid fuel cellaccording to claim 1, wherein said auxiliary electrode comprises apositive electrode material.
 6. The hybrid fuel cell according to claim5, wherein said auxiliary electrode is a nickel hydroxide positiveelectrode.
 7. A hybrid fuel cell including one or more electrochemicalcell units, said electrochemical cell units each comprising: anauxiliary electrode having a first side and a second side; a firstconsumable anode and a second consumable anode; and a first cathode anda second cathode, said first cathode and said second cathode each havingan oxygen contacting surface and an electrolyte contacting surface; afirst battery separator and a second battery separator; and a first gasdistributor plate and a second gas distributor plate; said auxiliaryelectrode being positioned such that said first battery separator isdisposed adjacent to said first side of said auxiliary electrode andsaid second battery separator is disposed adjacent to said second sideof said auxiliary electrode; said first consumable anode being disposedadjacent to said first battery separator opposite said auxiliaryelectrode and said second consumable anode being disposed adjacent tosaid second battery separator opposite said auxiliary electrode; saidfirst electrolyte distributor plate being disposed adjacent to saidfirst consumable anode opposite said first battery separator and saidsecond electrolyte distributor plate being disposed adjacent to saidsecond consumable anode opposite said second battery separator; saidfirst cathode being disposed adjacent to said first electrolytedistributor plate opposite said first consumable anode such that saidelectrolyte contacting surface of said first cathode faces said firstconsumable anode and said second cathode being disposed adjacent to saidsecond electrolyte distributor plate opposite said second consumableanode such that said electrolyte contacting surface of said secondcathode faces said second consumable anode.
 8. The hybrid fuel cellaccording to claim 3, wherein said conductive material comprisesgraphite or graphitized carbon.
 9. The hybrid fuel cell according toclaim 1, wherein said first cathode and said second cathode eachcomprise a carbon matrix with an active catalyst material catalytictoward the dissociation of molecular oxygen dispersed therein.
 10. Thehybrid fuel cell according to claim 9, wherein said active catalystmaterial is selected from silver, silver alloys, silver oxide, cobalt,cobalt oxide, cobalt manganese oxide, nickel, manganese oxide, manganesedioxide, pyrolyzed macrocyclics, or combinations thereof.
 11. The hybridfuel cell according to claim 9, wherein said first cathode and/or saidsecond cathode further comprise a peroxide decomposing material.
 12. Thehybrid fuel cell according to claim 11, wherein said positive electrodematerial comprises 75 to 85 weight percent of a positive electrodeactive material, 0.0 to 10 weight percent cobalt, 0.0 to 10 weightpercent cobalt oxide, and 0.0 to 4.0 weight percent of a bindermaterial.
 13. The hybrid fuel cell according to claim 11, wherein saidpositive electrode active material is selected from nickelhydroxide/nickel oxyhydroxide, copper oxide, silver oxide, manganesedioxide, or combinations thereof.
 14. The hybrid fuel cell according toclaim 11, wherein said auxiliary electrode is a silver electrode. 15.The hybrid fuel cell according to claim 7, wherein said first consumableanode and said second consumable anode each comprise an anode activematerial including zinc, cadmium, magnesium, aluminum, iron, lithium, orcombinations thereof.
 16. The hybrid fuel cell according to claim 15wherein said first consumable anode and said second consumable anodecomprise 90 to 99 weight percent of said anode active material and 1 to10 weight percent of a binder material.
 17. The hybrid fuel cellaccording to claim 7, wherein said first cathode and said second cathodeeach comprise a carbon matrix with an active catalyst material catalytictoward the dissociation of molecular oxygen dispersed therein.
 18. Thehybrid fuel cell according to claim 17, wherein said active catalystmaterial is selected from silver, silver alloys, silver oxide, cobalt,cobalt oxide, cobalt manganese oxide, nickel, manganese oxide, manganesedioxide, pyrolyzed macrocyclics, or combinations thereof.
 19. The hybridfuel cell according to claim 17, wherein said first cathode and/or saidsecond cathode further comprise a peroxide decomposing material.
 20. Thehybrid fuel cell according to claim 7 wherein said auxiliary electrodecomprises a positive electrode material.
 21. The hybrid fuel cellaccording to claim 20, wherein said positive electrode materialcomprises 75 to 85 weight percent of a positive electrode activematerial, 0.0 to 10 weight percent cobalt, 0.0 to 10 weight percentcobalt oxide, and 0.0 to 4.0 weight percent of a binder material. 22.The hybrid fuel cell according to claim 20, wherein said positiveelectrode active material is selected from nickel hydroxide/nickeloxyhydroxide, copper oxide, silver oxide, manganese dioxide, orcombinations thereof.
 23. The hybrid fuel cell according to claim 20,wherein said auxiliary electrode is a nickel electrode.
 24. The hybridfuel cell according to claim 20, wherein said auxiliary electrode is asilver electrode.